The present invention relates to an airbag apparatus of a vehicle having an airbag that inflates and deploys to protect an occupant in response to impact on the vehicle from behind and, more particularly, to an airbag apparatus that deploys and inflates, behind the rearmost seat, an airbag accommodated in an accommodation portion, which is provided in the space over the ceiling of the passenger compartment.
A rear airbag apparatus is effective in protecting an occupant seated on a rearmost seat when a vehicle is hit by another vehicle from behind and receives impact from behind. The airbag apparatus includes an airbag that deploys and inflates at a position between the rearmost seat and the rear window glass.
Like other types of airbag apparatus, the rear airbag apparatus has an inflator and an airbag as its main components. The inflator and the airbag, which is folded compactly, are accommodated in an accommodation portion provided in the space over the ceiling of the passenger compartment. If the vehicle is hit from behind and receives impact from the rear, the inflator supplies inflation gas to the airbag. The gas causes the airbag to shoot out of the accommodation portion into the passenger compartment. The airbag then deploys and inflates toward the space between the rearmost seat and the rear window glass.
The airbag is arranged between the head of the occupant seated on the rearmost seat and the rear window glass so as to isolate the head of the occupant from the rear window glass. The airbag absorbs the impact applied to the vehicle from behind and reduces the influence on the occupant by flying objects that may enter the passenger compartment from behind the vehicle. Also, change in the posture of the occupant in a rearward direction is suppressed by the airbag.
Japanese Laid-Open Patent Publication No. 2007-302096, for example, discloses this type of airbag apparatus. The apparatus includes a plurality of inflatable portions and a non-inflatable portion formed by fabric that connects each adjacent pair of the inflatable portions. While the inflatable portions are deployed and inflated by inflation gas at a position beside a headrest of a rearmost seat, the non-inflatable portion is deployed behind the headrest without inflating. The non-inflatable portion is provided for the following purposes: reducing the volume of the airbag in a deployed and inflated state; reducing the volume and the costs of the inflator; and improving the occupant protection performance by increasing the speed at which the airbag is deployed and inflated.
In the airbag apparatus, the airbag deploys and inflates rearward and diagonally downward while deploying and inflating in the direction of the width of the vehicle, or applying tension to the non-inflatable portion in the direction of the width of the vehicle. At this stage, the non-inflatable portion, while deploying, may contact the headrest of the rearmost seat. If such contact occurs, the non-inflatable portion interferes with the headrest, making it difficult for the non-inflatable portion to extend beyond the headrest and to deploy appropriately behind the headrest. Specifically, the interference between the non-inflatable portion and the headrest restricts outward deployment and inflation of the airbag in the direction of the width of the vehicle. This attenuates the intensity of the outward deployment and inflation of the airbag.
Particularly, because of recent demands for larger passenger compartment, it is more and more difficult to ensure the accommodation portion for the airbag in a rear end portion of the space over the passenger compartment ceiling. Accordingly, the accommodation portion may be arranged at a position forward of the vehicle compared to conventional cases. In this case, the accommodation portion is moved forward away from the headrest. The above-described interference between the non-inflatable portion and the headrest occurs easily.